Breather device



Patented May 29, 1934 UNITED STATES BREATHER DEVICE Ernest F. Gygax, St. Louis, Mo., assgnor to Curtis Manufacturing Company, Wellston, Mo., a corporation of Missouri Application February 27, 1931, Serial No. 518,663

2 Claims.

This invention relates to piston machines of the type in which air, or the medium being compressed, finds its way into the crank case of the machine through joints between the piston and '5 cylinder, joints in the crank case and joints between the crank shaft and its bearings, with the result that when the volume of the crank case is being reduced, an objectionable or undesirable pressure builds up in the crank case and causes oil to escape from the crank case through the crank shaft bearings or other joints in the crank case. The invention is applicable to compressors, pumps, four-cycle internal combustion engines, and various other types of piston machines, but

it is not applicable to two-cycle internal combustion engines or piston machines of the kind in which it is necessary or desirable to create pressure in the crank case at some point or points in the cycle of operations of the machine.

The main object of my invention is to provide a novel means of simple design and inexpensive construction, for preventing pressure from building up in the crank case of a piston machine of the kind mentioned, to such an extent as to result in oil being forced out of the crank case through the crank shaft bearings or other joints in the crank case.

To this end I have devised a piston machine which differs from piston machines of conventional design, in that the piston or one of the pistons of the machine co-operates with an outlet leading from the crank case, to form a mechanically-operated crank case pressure relief, designed so that a mean effective vacuum, sulficient to overcome the tendency of oil to escape fom the crank case through joints in same, will be maintained in the crank case during the major portion of the cycle of operations of the machine.

Figure 1 of the drawing is a vertical sectional view of a single piston machine, for example, a compressor, constructed in accordance with my invention, showing the piston at the end of its downward stroke. i

Figure 2 is a similar view, showing the piston in approximately its midway position.

Figure 3 is a similar View, showing the piston at the end of its upward stroke.

Figure 4 is a vertical sectional View, of a twostage compressor provided with cylinders of different diameters, showing the large piston at the end of its upward stroke and the small piston at the end of its downward stroke.

Figure 5 is a sectional View of the machine illustrated in Figure 4, showing both pistons in their midway position; and

Figure 6 is a sectional View of said machina illustrating the large piston at the end of its downward stroke and the small piston at the end 00 of its upward stroke,

In Figures 1, 2 and 3 of the drawing which illustrates a single cylinder machine embodying my invention, A designates a cylinder that is combined with a crank case B in such a way that one end of said cylinder is always in direct communication with said crank case, and C designates a piston reciprocatingly mountedin said cylinder and actuated by a rod D that is connected to a crank on a crank shaft E. In the machine herein shown the cylinder A is disposed vertically. Therefore, I have referred to the two extreme positions of the piston as the end of the upward stroke and the end of the downward stroke of the piston, but I wish it to be understood that my invention is applicable to a machine provided with a horizontally-disposed cylinder or a cylinder arranged in some other position than a, vertical position. Y

The crank case is provided with an outlet thatv leads to or communicates with the atmosphere, and in the Vform of my invention herein illus-` trated said crank case outlet is formed by an opening F in the side Wall of the cylinder A, adjacent the lower end of same. The piston C is so disposed with relation to said opening F that it acts as a valve, cut-off device or closure which opens and closes said opening F, and thus establishes and cuts off communication between theA atmosphere and the interior of the crank case through said opening when the piston is in operation. In the machine shown in Figures 1, 2 and 3, aport G is formed in the skirt or side wall portion of the piston C at such a point that said port will register with the outlet open-A ing F during certain periods in the cycle of operations of the piston, and thus establish communication between the atmosphere and the interiorof the crank case. During all other periods or in all other positions of the piston a solid portion of the piston extends over the outlet openingF, and thus eiectively cuts off communication between the atmosphere and the interior of the crank case. The outlet opening F can be constructed and arranged in various ways without departing from the spirit of my invention. It is herein shown as having its outer end communicating with an external oil pocket H on the cylinder, which is in direct communication with the at-I mosphere atall times. In order to recover any 1.19

oil which may escape from the crank case into the oil pocket H, through the outlet opening F, an oil return hole L of relatively small diameter is formed in the bottom of the oil pocket H, so as to permit oil which iinds its way into said oil pocket to return to the crank case by gravity.

In the form of my invention herein illustrated an automatically operating valve L', preferably a spring-seated ball check valve, is associated with the oil return hole L. Said valve L opens automatically when the pressure in the crank case gets down to atmosphere and remains open while the pressure in the crank case is less than atmospheric pressure, thereby permitting the oil in the pocket H to return to the crank case. Whenever the internal pressure of the crank case reaches or exceeds atmospheric pressure, the valve L closes automatically, and thus prevents air from rushing out of the crank case through the oil return hole L, and spattering oil out of the pocket H. In the drawing I have exaggerated the size of the oil return hole L. In practice said hole L is actually of so small a diameter that only such v a small amount of air and oil combined can enter said hole as to little alect the sub-atmospheric condition in the crank case. In other words, the quantity of air that can enter the crank case through the oil return hole L when the valve L is unseated, is practically negligible as compared to the quantity of air that nds its way into the crank case past the piston during the compression stroke of the piston, it being a recognized fact that approximately 4% oi the air compressed in the cylinder of an air compressor will leak into 4the crank case past the piston, even when the piston is equipped with new piston rings. The area or size of the oil return hole Lis innitesimal as compared to the area of the joints in the crank vshaft bearings, joints of the crank case and joints between the piston and the side wall of its cylinder, and while I have stated that a valve L' is preferably used to close the oil return hole L when the internal pressure of the crank case reaches or exceeds atmospheric pressure, the valve L is not essential and may be omitted, Without interfering with or reducing the emciencyY of the novel crank case pressure relief above described.

The outlet port or opening F is so proportioned and arranged with relation to the stroke of the piston that said port F will be closed or covered by said piston before, at and after the period when the crank case volume is at maximum, and said port F will be opened or uncovered by the piston immediately before, at and immediately after the period when the crank case volume is at minimum. In other words, the average full area of the opening F in the cylinder and the opening G in the piston, are open only during that one iifth of each cycle immediately before, at and immediately after` the period when the volume of the crank case is at minimum. Thus, as shown in Figure l, the port or opening G in the side wall of the piston slightly overlaps the opening F and establishes communication between the atmosphere and the interior of the crank case when the piston is at theA end of its downward stroke and the volume of the crank case is at minimum, and when the volume of the crank case is at maximum and the piston C is at the end of its upward stroke, as illustrated in Figure 3, a solid portion of the piston laps over the outlet opening F and closes the same. During the upward stroke of the piston the outlet opening F remains closed during' the major portion of the stroke, and hence, the vacuum in the crank case increases and reaches maximum when the piston reaches the end of its upward stroke and when the volume of the crank case is at maximum. On the downward stroke of the piston the relatively high vacuum that exists in the crank case diminishes, and when the port G in the piston comes into registration with the opening F, any air which may have leaked into the crank case is permitted or caused to escape through the opening F.

From the foregoing it will be seen that the principle of operation of my improved machine is radically diierent from the principle of operations of conventional piston machines equipped with a crank case breather, and briefly described, may be said to consist in providing a short period of pressure relief for a crank case in which a relatively high vacuum is maintained during a substantial portion of the cycle of operations of the piston, the period of pressure relief being obtained by an outlet opening in the side wall of a cylinder of the machine and a co-acting portion of the piston in said cylinder, so constructed and arranged that the outlet will be open when the minimum crank case volume is being approached, and has been reached, and said outlet will be closed when the maximum crank case volume is being approached and has been reached.

In Figure 4 I have shown how my invention may be applied to a multi-stage compressor provided with a large cylinder A and a small cylinder A2. In such a machine the side wall of the small cylinder A2 is provided with an outlet opening F that leads to an external oil pocket H whose upper end communicates with the atmosphere and whose bottom is provided with an oil return hole I of relatively small diameter leading back to the crank case and equipped with an automatically operating valve I. The side wall or skirt portion of the piston C2 which reciprocates in the cylinder A2 is not provided with a port that is adapted to register with the outlet opening F to establish communication between the atmosphere and the interior of the crank case, as in the form of my invention shown in Figures l, 2 and 3, but instead, the outlet opening F is arranged at such a point in the side wall of the cylinder A2 that said opening lies in the zone of the piston C2 during a certain portion of the stroke of the piston and lies in a zone outside of the path of movement of the piston during the remainder of the stroke of the piston.

When the large piston C is at the end of its upward stroke, as shown in Figure 4, the internal volume of the crank Ycase is at maximum and the small piston C2 occupies such a position with relation to the outlet opening F, that yit closes said opening, and thus cuts 01T communication between the atmosphere and the interior of the crank case. During the succeedapproximately its midway position during its upward stroke, the small piston C2 returns to the zone of the breather opening, closing the same and keeping it in a closed condition as the maximum crank case volume is being approached and reached.

When the machine is in operation a relatively high vacuum is created in the crank case during the period in the cycle of operations when the volume of the crank case is being increased, and during the period of the cycle of operations when the volume of the crank case is being reduced, a pressure relief period is provided wherein any air that may have leaked into the crank case past the piston or through joints in the crank case or crank shaft bearings is permitted or caused to escape from the crank case to the atmosphere. Accordingly, in a piston machine embodying my invention there is never suiicient sustained pres sure in the crank case to cause oil to be forced outwardly through the crank shaft bearings or through joints in the crank case, and there is no liability of dirt or other foreign matter being drawn into the crank case and mixed with the oil in same, because the crank case outlet above referred to is maintained in a closed condition, thus cutting off communication between the interior of the crank case and the atmosphere, when the piston is moving in a direction to increase the volume of the crank case.

Devices of various designs and construction have heretofore been proposed for relieving the pressure of the crank case, but I believe that it is novel to utilize a piston or one of the pistons of a pump, compressor, four-cycle internal combustion engine, or other type of piston machine in which the accumulation of pressure in the crank case is objectionable, to govern or control an outlet opening leading from the crank case to the atmosphere, the said outlet opening being so proportioned and arranged with relation to the stroke of the piston which controls said opening, as to cut off communication between the atmosphere and the interior of the crank case during the major portion of the cycle of operations, but to provide a period of pressure relief for the crank case that is of slight duration as compared with the extent and duration of the vacuum that is created in the crank case during that portion of the cycle of operations when the volume of the crank case is being increased. The time of operation and extent of operation of the pressure relief device above described may be Varied to suit existing conditions, without departing from the spirit of my invention, but I prefer to so proportion the crank case outlet and time the piston that controls the same, that a substantially mean effective vacuum will be maintained in the crank case during the major portion of the cycle of operations of the machine.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A piston machine of the kind referred to provided with a crank case, a cylinder having one of its ends communicating with the interior of the crank case, said cylinder being provided in its side wall, adjacent the crank case, with a port, and a reciprocating piston in said cylinder that opens and closes said port, said port being so proportioned and so arranged with relation to the stroke of the piston that said port will be closed by said piston before, at and after the period when the crank case volume is at maximum, and said port will be opened by said piston, thus establishing communication between the atmosphere and the interior of the crank case through said port, immediately before, at and immediately after the period when the crank case volume is at minimum.

2. A piston machine of the kind referred to provided with a crank case, a cylinder having one of its ends communicating with the interior of the crank case, said cylinder being provided in its side wall, adjacent the crank case, with a port, and a reciprocating piston in said cylinder that opens and closes said port, said port being so proportioned and so arranged with relation to the stroke of the piston that said port will be closed by said piston during the major portion of the cycle of operations of the machine, and said port will be opened by said piston, thus establishing communication between the atmosphere and the interior of the crankcase through said port, only during that portion in the cycle of operations of the machine immediately before, at and immediately after minimum crank case volume.

ERNEST F. GYGAX. 

